These data provide optical observations that will be correlated with bathymetry and acoustic backscatter imagery
to develop a benthic habitat map of Brooks Banks. Refer to supplemental information for description of instrument and
survey.

Supplemental_Information:

Brooks Banks, located at 24.1N, 166.8W, are four neighboring flat-topped banks located northwest
of French Frigate Shoals. The four banks, from southeast to northwest, include Baby Brooks, East Brooks, Middle Brooks, and West Brooks and are estimated to be 13.6 million years old. The banks contain a total of 320 sq. km of reef habitat with depths less than 100 m.

Optical validation data were collected using the Tethered Optical Assessment Device (TOAD), a sled equipped with underwater
video cameras and lights. These data are used to provide ground-truth validation for benthic habitat maps
based on multibeam echosounder surveys and to gather additional information regarding benthic communities. Camera sled deployments were conducted at night and during the day. The camera sled was deployed off the starboard J-frame on NOAA
ship Hi'ialakai. The TOAD was lowered slowly to the bottom by a winch holding 360 m of cable and operated from a control
station in the dry lab of the ship. The TOAD operator monitored a live video feed from the camera and record data on a
video tape recorder.

Equipment Description: The TOAD sled body used for the data collection is constructed from a shortened Phantom ROV body with a tail piece added for stability.

The frame has been extensively modified from its original configuration and was equipped with two Deep Sea Power and Light Multi SeaCam 2060 color video cameras. One camera is mounted to point at approximately a 45 degree angle toward the seafloor and is the primary data collection instrument. The second camera is aimed straight ahead and the signal from this camera is fed to a second video monitor to provide warning of underwater
obstructions. The video signals from the sled are sent via coaxial conductors within a 360 m long and 19 mm diameter umbilical cable to a topside control unit. The cable between the sled and the surface includes an internal strength member to support the sled frame. The cable is paid out and recovered using a dedicated custom-built winch equipped with slip rings and powered by a 5 hp electric motor. The winch is controlled at the winch itself for sled deployments and recoveries. The rest of the time a remote controller located in the dry lab is used to enable the operator at the video console to adjust the sleds altitude. All TOAD surface components are located in the Dry Lab in an equipment rack
on the after bulkhead. Illumination is provided by two 250 W DeepSea Power & Light Multi-SeaLite model 1050 underwater
lights mounted on the sled frame. The lights are located on each side of the sled to provide the maximum possible
horizontal distance from the camera. An ORE Offshore model 4330B Multibeacon is attached to the sled to provide a
response to acoustic interrogations sent by the Hi'ialakai's Model 4410D-01 Trackpoint II Plus Ultrashort Baseline
acoustic tracking system. The sled is also equipped with a sonar altimeter to detect the height of the camera above
the seafloor, a pair of parallel lasers to determine the size/scale of viewed objects, a compass to determine the
sled heading and orientation, and a depth (pressure) sensor. Neither the altimeter nor the pressure transducer
functioned reliably during this cruise.

Data Files: Video data are recorded on a mini DV video tape recorder. The position of the camera sled is recorded
using Hypack Max version 6.2b survey software.

File naming convention: Each tow is given a name consisting of a 3-letter
designator for the island area followed by two-digit year and three-digit tow number. For example, during HI0804
(NOAA Ship Hi'ialakai's 4th cruise in calendar year 2008) the first tow was called FFS08001. Video tape labels and
paper log forms are annotated with the tow name. Data files recorded in Hypack software followed their CHS filename
format consisting of the year, the first two letters of the platform name, the Julian date, and the hour and minute
in which the file was started. For example, a file collected on July 18, 2005 (Julian date 199) aboard the Hi'ialakai
starting at time 1935 would be 2005HI1991935.

Time Correlation: All times are based on UTC. Four clocks were manually synchronized prior to starting data collection;
the clock in the on screen display that was used to annotate the video tape, in one of the video cassette recorders,
in the Trackpoint II system, and in the computer running the Hypack Max software. These clocks are set to UTC at the
beginning of each operation.

The horizontal position accuracy for the camera sled position is estimated at +/-20 meters. There are two primary sources of this error. The ship's positioning is based on GPS SPS, often called standalone or non-differential GPS positioning. SPS has a measured accuracy of under 5 meters. The position of the GPS antenna is referenced to the ship's granite block. The second and larger primary source of error is uncertainty associated with the sled's position as reported by the Trackpoint II acoustic tracking system, which is also referenced to the granite block.

Lineage:

Process_Step:

Process_Description:

After a tow is completed the video tape data is reviewed by spot-checking the master and backup
tape to verify that data were recorded. Raw data files recorded using Hypack Max software include time, horizontal
position, and ship's heading information are copied from the acquisition computer to the data archive. Tow-specific
metadata are recorded in the data archive in the same location as the raw data, in a spreadsheet that was then referred
to in creating metadata records of each island where data were collected during the cruise. Raw data files are exported
as comma-delimited text files which were then imported into ArcGIS v9.2 and saved as shapefiles.

These data are not to be used for navigational purposes. NOAA makes no warranty regarding these data, expressed or implied, nor does the fact of distribution constitute such a warranty. NOAA cannot assume liability for any damages caused by any errors or omissions in these data, nor as a result of the failure of these data to function on a particular system.

Standard_Order_Process:

Digital_Form:

Digital_Transfer_Information:

Format_Name: ASCII

Format_Information_Content:

Each comma-delimited record contains information on the UTC date and time, horizontal position of the sled, and heading of the ship over the period of time that the camera sled is in the water.